A formal test using agent-based models of the circumscription theory for the evolution of social complexity

The emergence of social complexity in human societies is a long-debated topic in archaeology, with competing hypotheses proposed and argued for using archaeological evidence. However, formal testing of these hypotheses is generally lacking. Here, we present and analyse an agent-based model to test the effect of environmental, resource, and social barriers to population movement – collectively known as ‘circumscription’ – on the rate of hierarchy formation. The results show that social circumscription is the largest driver of social complexity by increasing proximity between settlements. Environmental and resource circumscription can negatively impact the emergence of social complexity when the conditions separate the population spatially but can amplify social complexity when the conditions increase proximity between settlements. In providing a detailed test of the assumptions and predictions of circumscription theory, our abstract model provides insight into the conditions that are most likely to result in the emergence of social complexity in the real world.